The disclosure relates to an eccentric bearing having the features described below. The eccentric bearing according to the disclosure is provided, in particular, for an electrohydraulic piston pump unit of a hydraulic brake system of a motor vehicle. Such pump units are used to generate a hydraulic brake pressure for brake actuation in slip-controlled and/or power brake systems.
Known eccentric bearings have an eccentric shaft which is mounted integrally, or rigidly in some other way, and eccentrically on a motor shaft of an electric motor or on an output shaft of a transmission that can be driven by the electric motor. Arranged on the eccentric shaft is a rolling contact bearing having a bearing ring concentrically surrounding the eccentric shaft and having rolling elements arranged around the shaft in a gap between the eccentric shaft and the bearing ring, generally but not necessarily at equal spacings. The rolling elements are usually rollers or needles although they can also be other rolling elements, e.g. balls. The bearing ring can be understood as an outer ring, and there can be an inner ring, said inner ring being press fitted onto the eccentric shaft for example. However, an inner ring is not necessary: the rolling elements can also roll directly on the eccentric shaft. One or more pump pistons of the pump piston unit rest by means of the ends thereof against the outside of the bearing ring. The pump pistons are pressed into contact with the bearing ring from the outside by springs, for example.
When driven in rotation, the eccentric shaft performs a movement on an orbital path owing to its eccentricity, rotating about itself in the process. Owing to the movement of the eccentric shaft on the orbital path, the bearing ring also moves on an orbital path or on the same orbital path and thereby drives the pump pistons resting externally against it to perform the desired reciprocating motion in order to deliver brake fluid or, more generally, fluid through alternate suction and displacement, as known from piston pumps. Owing to its rolling contact bearing arrangement, the bearing ring does not rotate with the eccentric shaft.
In electrohydraulic piston pump units for hydraulic brake systems of motor vehicles, the eccentric bearings convert a rotary motion of an electric motor or of an output shaft of a transmission into a reciprocating motion in order to drive the pump pistons.